The interest of these nanostructures leads to control the physical properties of the CSQDs by varying their size/thickness, and leads to adjust their energy levels, as well as the intra- or inter-band transitions by absorption or emission. In addition, the advances in materials science have enabled the production of a new generation of heterostructures called core/shell quantum dots (CSQDs) and multi-layer quantum dots with different geometrical shapes and material compositions 12, 13, 14, 15. The interest in these particular nanostructures lies in their novel and exceptional electronic, magnetic, and optical properties 9, 10, 11. The QDs are considered as carrier systems of almost zero dimension, since the motion of charge carriers in these structures is limited to well-defined energy values. Which have been the most studied, both from a theoretical and experimental point of view, because of the numerous possibilities of application in electronic and optoelectronic devices 1, 2, 3, 4, 5, 6, 7, 8. In recent years, improved material growth techniques have enabled the practical realization of semiconductor-based nanoscopic structures such as quantum wells (QWs), quantum dots (QDs), and quantum rings (QRs).
The findings might be used to modify the electronic and excitonic properties in nanomaterials science. In addition, the transition from a type-A to a type-B confinement system has been observed. Also, The binding energy of an on-center (off-center) donor atom is greater (weaker) than that of the exciton, whatever the structure of the confinement potential. So, the external potential effect is more significant when the first shell thickness and potential are small. Moreover, the confinement potential effect of the first material on the energies is more pronounced when their thickness is large and the core radius is small. Our results show that the donor atom and exciton binding energy, as well as the electron energy, strongly depend on the core radius, first shell thickness, confinement potentials of the barrier materials, and their structures (A and B). To obtain the ground state quasiparticles energies, we have used the variational technique. Within the effective mass and parabolic band approximation, the 3D time-independent Schrödinger equation has been resolved. The confinement of charge carriers in CSSQD with two finite confinement potentials models of the barrier materials are studied. The effects of confinement potentials of the first and second materials, core size and first shell thickness on the confinement of electron, electron-donor atom, and exciton in cylindrical core/shell/shell quantum dot (CSSQD) are studied taking into account the finite confinement potential model.
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